title: Emodin induces human T cell apoptosis in vitro by ROS-mediated endoplasmic reticulum stress and mitochondrial dysfunction.
abstract: OBJECTIVE
  To elucidate the molecular mechanisms underlying the immunosuppressive effects of emodin isolated from Rheum palmatum L.
  
  
  METHODS
  Human T cells were isolated from the peripheral venous blood of 10 healthy adult donors. Cell viability was analyzed with MTT assay. AO/EB and Annexin V/PI staining and DNA damage assay were used to detect cell apoptosis. Fluorescence staining was used to detect the levels of ROS, the mitochondrial membrane potential and intracellular Ca(2+). Colorimetry was used to detect the levels of MDA and total SOD and GSH/GSSG ratio. The expression and activity of caspase-3, -4, and -9 were detected with Western blotting and a fluorometric assay. Western blotting was also used to detect the expression of Bcl-2, Bax, cytochrome C, and endoplasmic reticulum (ER) markers.
  
  
  RESULTS
  Emodin (1, 10, and 100 μmol/L) inhibited the growth of human T cells and induced apoptosis in dose- and time dependent manners. Emodin triggered ER stress and significantly elevated intracellular free Ca(2+) in human T cells. It also disrupted mitochondrial membrane potential, and increased cytosolic level of cytochrome C, and the levels of activated cleavage fragments of caspase-3, -4, and -9 in human T cells. Furthermore, emodin significantly increased the levels of ROS and MDA, inhibited both SOD level and GSH/GSSG ratio in human T cells, whereas co-incubation with the ROS scavenger N-acetylcysteine (NAC, 20 μmol/L) almost completely blocked emodin-induced ER stress and mitochondrial dysfunction in human T cells, and decreased the caspase cascade-mediated apoptosis.
  
  
  CONCLUSIONS
  Emodin exerts immunosuppressive actions at least partly by inducing apoptosis of human T cells, which is triggered by ROS-mediated ER stress and mitochondrial dysfunction.
authors.affiliation: Department of Hepatobiliary Surgery, The First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an 710061, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Qu
authors.forename: Nai-ying
authors.initials: NY
authors.lastname: Shen
authors.forename: Xin-sen
authors.initials: XS
authors.lastname: Xu
authors.forename: Hai-bo
authors.initials: HB
authors.lastname: Su
authors.forename: Ji-chao
authors.initials: JC
authors.lastname: Wei
authors.forename: Ming-hui
authors.initials: MH
authors.lastname: Tai
authors.forename: Fan-di
authors.initials: FD
authors.lastname: Meng
authors.forename: Lei
authors.initials: L
authors.lastname: Zhou
authors.forename: Yue-lang
authors.initials: YL
authors.lastname: Zhang
authors.forename: Chang
authors.initials: C
authors.lastname: Liu
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004642:Emodin / Q000494:pharmacology*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects* / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013601:T-Lymphocytes / Q000187:drug effects* / Q000502:physiology
chemical_list: D017382:Reactive Oxygen Species; D004642:Emodin